Question

void run() {
    ...
    if (done) return cancel();
    ...
}

where cancel() return void. This won’t compile… and I can almost understand why. But if I want to return a void from a void, why not? Instead, I end up writing something like this:

if (done) {
    cancel();
    return;
}

I’m not looking for code style suggestions, I want to know why Java expressly prohibits this type of void return. Any info is appreciated, thanks.

Answer 1

A return statement with an expression returns the value of that expression. The type of cancel() is a void expression – it doesn’t have a value.

Logically you want to execute cancel(), and then return – so that’s what you have to say. The two actions (calling cancel() and then returning) are logically distinct.

Now Java could have a sort of “unit” type instead of void – but that would affect rather more than just return values.